Method for producing etched circuits

Abstract

Two sided printed circuit boards with very small rings surrounding the plated though holes can be produces by starting with a through-plated copper laminate, and coating it with a liquid negative electrodeposition photo-resist. The coated photo-resist is exposed to light through a mask set up so that the light does not shine on the through-platings. The non-crosslinked photo-resist is subsequently removed. A metal or a metal alloy resist is laid down by electrodeposition on those surfaces from which the non-crosslinked photo-resist has been removed. Finally, the crosslinked photoresist material is removed and the exposed copper laminate is treated with a copper-etching solution to completely remove the copper surface that has been uncovered.

What is claimed is:  
     
       1. A method for producing double-sided printed circuit boards having through-platings, the method comprising the steps of: 
       (A) coating both sides of a through-plated copper laminate using a negative photo-resist;  
       (B) exposing selected portions of both sides of the photo-resist to light through a mask, wherein the through-platings and small regions surrounding the through-platings are not exposed to light;  
       (C) removing portions of the photo-resist coating that were not exposed to light in step (B);  
       (D) applying etch-resist to the through-plated copper laminate-by electrodeposition wherein the etch-resist is a metal or a metal alloy;  
       (E) removing portions of the photo-resist coating that were exposed to light in step (B), so as to uncover underlying copper;  
       (F) removing copper from portions of the through-plated copper laminate that are not protected by the etch-resist so that only very small rings of copper or no rings of copper remain around the through-platings; and  
       (G) removing the etch-resist.  
     
     
       2. The method of  claim 1 , wherein the small region is about 0.05 mm wide. 
     
     
       3. The method of  claim 1 , wherein the small region is an annular ring that is about 0.05 mm wide. 
     
     
       4. The method of  claim 1 , wherein the small region is an annular ring with an outer diameter of about 0.3 mm. 
     
     
       5. The method of  claim 1 , wherein the very small ring of copper is about 0.025 mm wide. 
     
     
       6. The method of  claim 1 , wherein the very small ring of copper is less than about 0.025 mm wide. 
     
     
       7. A method for producing double-sided printed circuit boards having through-platings, the method comprising the steps of: 
       (A) applying etch-resist to a through-plated copper laminate by electrodeposition in a pattern that includes small annular rings around the through-platings of the copper laminate;  
       (B) removing copper from portions of the through-plated copper laminate that are not protected by the etch-resist that was applied in step (A) so that either very small rings of copper or no rings of copper remain around the through-platings; and  
       (C) removing the etch-resist.  
     
     
       8. The method of  claim 7 , wherein the etch-resist is a metal or a metal alloy. 
     
     
       9. The method of  claim 7 , wherein the small annular rings are about 0.05 mm wide. 
     
     
       10. The method of  claim 7 , wherein the small annular rings have an outer diameter of about 0.3 mm. 
     
     
       11. The method of  claim 7  wherein the etch-resist is a metal or a metal alloy, and the small annular rings are about 0.05 mm wide and have an outer diameter of about 0.3 mm. 
     
     
       12. The method of  claim 7 , wherein the very small rings of copper are about 0.025 mm wide. 
     
     
       13. The method of  claim 7 , wherein the very small rings of copper are less than about 0.025 mm wide. 
     
     
       14. The method of  claim 7  wherein the etch-resist is a metal or a metal alloy, and the small annular rings are about 0.05 mm wide, and the very small rings of copper are about 0.025 mm wide. 
     
     
       15. The method of  claim 7  wherein the etch-resist is a metal or a metal alloy, and the small annular rings are about 0.05 mm wide, and the very small rings of copper are less than about 0.025 mm wide.